There is no power in the Constitution or case law to undo a pardon, but President Trump on Sunday claimed pardons issued by former President Biden were void, in a social media post that embraced a baseless right-wing conspiracy theory.

Trump Says Biden’s Pardons are ‘Void’ and ‘Vacant’ Because of Autopen
The use of the autopen, a device that reproduces signatures and is ubiquitous in government and business, is ordinarily uncontroversial. There is no power to undo a pardon in the Constitution or case ...